The present application generally relates to a memory system.
In an information processor such as a computer, a DRAM (Dynamic Random Access Memory) with high density that is operated at high speed is widely used.
However, the DRAM is a volatile memory where information is erased when the power is turned off. So, a non-volatile memory where information is not erased is needed.
As a candidate of the non-volatile memory, a magnetoresistive random access memory (MRAM) where information is recorded by magnetization of a magnetic body is focused on and is under development.
A method of recording to the MRAM includes a method of reversing magnetization by current magnetization or a method of reversing magnetization by directly implanting spin-polarized electrons into a recording layer (for example, see Patent Document 1).
As the method, spin implantation magnetization reversal is focused on because a record current can be decreased as the device size gets smaller.
Furthermore, in order to miniaturize the device, a method of using a perpendicular magnetization film where a magnetization direction of a magnetic body is directed to a perpendicular direction is studied (for example, see Patent Document 2).
Non-Patent Document 1 discloses a reversal time equation of a spin implantation magnetization reversal element using a perpendicular magnetization film.
Patent Document 1: Japanese Patent Application Laid-open No. 2004-193595
Patent Document 2: Japanese Patent Application Laid-open No. 2009-81215
Non-Patent Document: R. H. Koch et al, Phys. Rev. Lett. 92, 088302(2004)